


possession

by reset-after-reset (relvius)



Category: Undertale (Video Game)
Genre: Dubious Consent, Multi, No Genitals, Slime, Tentacles
Language: English
Status: Completed
Published: 2015-11-07
Updated: 2015-11-07
Packaged: 2018-04-30 12:21:45
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 1,877
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/5163665
Author URL: https://archiveofourown.org/users/relvius/pseuds/reset-after-reset
Summary: <blockquote class="userstuff">
              <p>“Hey, I’m not looking for a fight.” Flowey tilted his head to the side in a way that Sans imagined was meant to look cute. Sans wasn’t in the mood. “I just want some information. I want to learn about Gaster.”</p>
            </blockquote>





	possession

**Author's Note:**

> thanks to epochryphal for betaing and suggesting Flowey/Sans/Gaster at all

Sans woke up covered in vines.

He was in the chair in his workshop, napping after who knew how long of poring over arcane theories and numbers. There were plants growing from numerous vents and other cracks in the wall, twisting and writhing as Sans watched them. He could only move his head; his limbs were pulled down, immobilized.

That wasn’t what had woken him up, though. There was a familiar-sounding voice that he knew he hadn’t heard before. “Hey, bonehead, I’m talking to you.”

Sans expected some kind of large monstrous figure. What he saw on the table in front of him, however, was a small golden flower, first scowling at him, then suddenly breaking into a smile. The sight threw Sans off momentarily. A talking flower? An unsettling sinking feeling crawled through his chest, and it wasn’t just the vines making their way through his ribcage. A memory of a memory warning him about talking flowers, maybe.

“Howdy! I’m Flowey the flower! Boy, you sure have been busy, haven’t you?” The flower leaned over the notes sprawled across the desk. It was more of an intrusion than the simple presence of someone else in his workshop was, and Sans glowered. A flower couldn’t be all that durable, though; Sans was already preparing a flurry of bones to tear those petals apart.

“Hey, I’m not looking for a fight.” Flowey tilted his head to the side in a way that Sans imagined was meant to look cute. Sans wasn’t in the mood. “I just want some information. I want to learn about Gaster.”

Sans’ concentration faltered. “how--?” With a snort, he again readied an attack, but held off on firing quite yet. “how do you know that name?”

“It sure has been hard to find anything out,” Flowey went on. “All I know is that he used to exist, and then he didn’t. I want to know why.”

As curious as he was, Sans wasn’t keen on his position of interrogatee. He unleashed his attack, a wall of bones converging on Flowey’s position. When the attack clattered aside, the flower was gone -- but moments later, a new vine was snaking its way up Sans’ ribcage. It wrapped around his clavicle, then rose out of his collar.

“That kind of stung, you know,” Flowey said. Sans couldn’t quite turn his head enough to see the flower now sprouting from his shoulder, but he could glimpse a sharp, toothy expression very different than how Flowey was smiling before. “You’re always so stubborn, Sans. I just want to ask a few questions.” Another vine found its way through Sans’ shoulders, then around his neck and up through the base of his skull. It was a sensation almost like choking, if Sans had needed to breathe. “What happened to him? Why is he outside any timeline?”

All at once, the room went cold, and Sans was pretty sure that it wasn’t just the unpleasant chills from having vines throughout his body. A hand gripped Sans’ shoulder firmly, and for once, Gaster’s presence was a relief. His voice echoed from everywhere and nowhere, not quite in any language but still perfectly understandable: LET HIM GO.

All the vines idly sliding through Sans’ body stopped. “Oh! You must be Gaster!”

LET HIM GO. LET HIM GO.

“You’re very unpredictable, you know. I’ll come across someone talking about you, then next reset, they’re gone!”

Sans had had the sinking feeling that resetting was involved somehow. That flower was way more powerful -- and dangerous -- than he looked. He glanced up to see a dark void looming over him. Gaster’s face was contorted, scowling and enraged and dark. Reality seemed a little looser around him -- his features shifted and flickered. It made Sans quake, even knowing that the fury wasn’t directed at him. Still, Gaster was rough in the way two of his hands materialized around one of Sans’ arms and tried to yank upwards, but the vines didn’t budge.

“shit, stop-- gaster, stop! you’re gonna rip my arm off.” The pulling stopped, but the hands held firm. Sans groaned at the tingling pain, and tried to speak ignoring the creeping intrusion into his skull. “look, bud, we’re trying to figure out what happened ourselves. we--”

“I think I’ll talk to Gaster. Seems like he’d know better, right, Gaster?”

I AM NOT TALKING TO YOU. There was an echoing snarl in his voice, something more animal than like the scientist Sans once knew. LEAVE. LEAVE.

Flowey laughed. “You know, you sound jealous.” Sans felt a vine press at the roof of his mouth and another move through his pelvis. He grit his teeth and tried to jerk away, but the plant was as tough as metal. “You’re not getting rid of me without hurting him. Now, I want to know--” Flowey suddenly yelped. Gaster had dove down, black tar spearing down through Sans’ collarbones. Sans couldn't help but let out a small sound himself.

OUT. Gaster was quick to fill Sans’ chest with himself. If Sans hadn't already been sitting, immobile, he would have gone weak-kneed.

“gaster, what--”

“Wow!” Flowey’s voice came from Sans’ other side now -- he must have ducked away to avoid the onslaught. “You really are jealous, huh? You know--” Flowey’s voice dropped to a hissing whisper-- “Sans and I have gotten very close in some timelines.”

It struck Sans as amusing, a bizarre feeling given the danger he knew he was in. One of those other Sans-es didn’t have the best taste, apparently. Although, maybe it wasn’t personality that this other Sans was interested in. Tendrils inched through Sans’ pelvis, and if Sans let himself go, it felt damn good, between the vines constricting in the right places and Gaster’s presence in his ribs. And why not just let go? Flowey certainly wasn’t planning on letting go himself anytime soon, and Gaster -- well. Gaster was Gaster, unpredictable and emotional and without much of a concept of personal space. Sans let his head rest back against the chair.

“Really? You like this?” It apparently wasn't the reaction Flowey was expecting. “Freak.”

“you’ve got me beat,” Sans said, attempting a shrug. “might as well enjoy getting beaten off, right?”

The black in his chest suddenly twisted in a way that wasn’t entirely painful. His vision went white and red. THIS IS NOT A JOKE.

Sans let out a breathy laugh at the way his head spun, at how that bit of aggression and pain was all he needed for every inch of his body to light up with sensation and need. Maybe laughing wasn’t the best idea, though: Gaster gave a short hiss and a hand materialized around Sans’ chin and forced it up -- there went the last bit of movement that Sans could fully control. Another slimy appendage grew from Gaster’s body, reeling back snakelike for a moment before shooting down into one of Sans’ eyes. It filled his skull, sending the world spinning once more; Sans spasmed in his binds, and nothing much mattered anymore than the writhing ooze inside him, pushing against bones in ways both painful and pleasurable, and the light touches of vine in sensitive places.

“Wow.” Flowey’s voice next to his earbones sounded distant. “Gross.”

“oh fuck,” Sans gasped, shivering. Gaster was moving down though his body now at a creeping pace compared to his earlier movements, sliding across vertebrae then pelvis then trickling down his thigh bones. Where Gaster touched, the plant moved as well, shifting or tightening or relaxing. And Sans couldn’t move with at all except to weakly pull against his binds and try to angle his hips to follow the touches.

HE IS MINE. The way Gaster’s voice rung out made the smallest of vibrations inside Sans -- nearly imperceptible, but still driving him mad.

“Tell me, could you always do this? Or is this also one of your strange timeline powers?” Flowey hummed. “I still have questions for you, Gaster.”

Gaster remained silent as the hands that were previously grabbing at Sans’ arm moved to his front, one lifting up his shirt and the other inching down his shorts. The cool air against his hips was yet another maddening sensation -- Sans let out a long whine. The hand at his chin also loosened and brushed up Sans’ face like a caress. It only took a light touch to push open Sans’ mouth, ooze dripping out, then a thumb began to rub light circles into the roof of his mouth. The vine that was there responded by moving to the side and sprouting from the corner of Sans’ mouth.

IT IS NOT IMPORTANT. I AM OF NO CONSEQUENCE TO YOU.

All of Flowey moved at once. “It is important! You’re outside the timelines!”

EXACTLY. A low growl. NOW LEAVE.

Sans was far past the point of being able to process what they were talking about -- it was just words -- but he could tell Flowey was excited.  “You’re unpredictable! You don’t understand how important that is!”

Gaster was rough in grabbing Sans’ pelvis, fingers digging into places that Gaster clearly knew would make Sans scream. And he did, muffled only slightly by the palm of Gaster’s hand. LEAVE. Where the hand in his hips moved, bone would first be exposed to cool air then covered once more in warm, almost too-hot tar. HE IS MINE. Fingernails (or maybe claws) scraped against him, leaving small grooves to be filled by stinging pain. The thick vines through loops of bone held even that part of him perfectly still, even as he desperately tried to buck against Gaster’s fingers.

Sans was peaking quickly. He was a mess, whimpering and moaning and writhing where he could. Trying to focus his scattered attention on one part of his body just led to movement in another: Gaster grabbing into his hips, the twisting fullness in his chest, Flowey wrapped around his spine and neck, the almost delicate touches on his mouth. He lost all sense of anything except pleasure as he came. Rolling through what felt like endless waves of orgasm, he could hear his voice swearing,  “fuck, oh fuck, gaster, gaster, fuck…”

When the sensations didn't stop, Sans swore he was going to unravel. Flowey was still crawling through his body, Gaster still roughly scratching and petting him. His bones could only handle so much. He became dimly aware, however, that the vines were unwinding themselves, granting movement to shivering and sore limbs. And perhaps in response, Gaster’s movements slowed until he was just holding Sans in his warmth.

“Boy, that sure was fun, wasn't it?” Maybe Sans was imagining it, but Flowey sounded a bit breathless himself. “But you're clearly in no condition to tell me anything. So, uh, I'll be back later. Pleased to meet you, Gaster.” The flower ducked out of Sans’ shoulder, and the last of the vines retreated.

Sans groaned at having to exert some amount of effort in order to not slide inelegantly onto the floor. But, it was only moments before Gaster spun the chair around. His face was no longer contorted in rage, but rather the blank, slightly too wide smile that often hid what he might have actually been feeling. MINE. MINE. MINE, he growled before diving into Sans once more.


End file.
